1. Field of the Invention
The invention relates to a color image forming apparatus such as a color copying machine, a color printer, and a color facsimile using an electrophotographic system, in particular, to improvement of a color image forming apparatus, which reclaims toner recovered by a cleaning unit, in forming an image.
2. Description of the Related Art
Conventionally, as this kind of a color image forming apparatus such as a color copying machine and a color printer, and a color facsimile using an electrophotographic system, a tandem-type color image forming apparatus has been proposed and come into the market already. In the tandem type color image forming apparatus, four image forming units respectively corresponding to yellow (Y), magenta (M), cyan (C), and black (K) are arranged in series, yellow (Y), magenta (M), cyan (C), black (K) toner images formed by the image forming units are primarily transferred onto an intermediate transfer belt in a superposed manner, then a full-color toner image generated by overlaying these single-color toner images on the intermediate transfer belt is secondarily transferred onto a recording medium all at once, and thereafter the full-color toner image is fixed on the recording medium to form a full-color image.
In the color image forming apparatus, a method including recovering toner remaining on the surface of the intermediate belt and a photoconductor drum by a cleaning unit, and returning the toner recovered by the cleaning unit to a black developing unit to reclaim the recovered toner has been proposed.
According to the above method, foreign matters such as paper debris are attached to the surface of the intermediate transfer belt when the intermediate transfer belt is in contact with a sheet in the second transfer position. The foreign matters attached to the intermediate transfer belt are recovered by the cleaning unit of the intermediated transfer belt, together with the residual toner after the transfer. The toner recovered by the cleaning unit for the intermediate transfer belt is supplied to a developing unit, and then is reclaimed. If the toner is reclaimed, a trimmer of the developing unit is jammed by the foreign matters such as paper debris mixed in the toner. Otherwise, the foreign matters are attached to a background part of a developed image, thereby causing image defects such as color dots.
A method to solve this problem has already been disclosed that, before recovering residual toner after the transfer by the cleaning unit for the intermediate transfer belt, only the foreign matters such as paper debris attached to the surface of the intermediate transfer belt are removed, or the foreign matters such as paper debris are removed from toner recovered by the cleaning unit.
JP2002-311669A discloses the following device. A color image forming device for removing adhering paper has been disclosed which forms a color image on a sheet by transferring toner images formed on respective image carriers of a plurality of imaging means to form a composite toner image on an intermediate transfer body, and then transferring the composite toner image. The device for removing adhering paper is provided in the color image forming device having a toner recycling device, which reuses residual toner after the transfer by putting the residual toner after the transfer back to a developing unit used by the black imaging means among the imaging means. The device for removing adhering paper is provided on upper stream of an image transfer position in a sheet conveyance path.
A color image forming apparatus that includes a plurality of image forming units having at least an image carrier and a developing unit, a transfer unit, which transfers a toner image formed on the image carrier onto a transfer material, and a cleaning unit, which scrapes and recovers residual toner adhering to the image carrier after the image carrier passes through the transfer unit have been disclosed. In the color image forming apparatus, the cleaning unit has a plurality of cleaning members, which scrape and recover residual toner adhering to the image carrier, and toner conveyance paths corresponding to the toner recovered by the respective cleaning members. At least one of the plurality of toner conveyance paths forms a recycled-toner supplying path to a developing unit, and the other toner conveyance paths are connected to a disposal system.
Further, an image forming apparatus that includes a plurality of image carriers, charging and exposing means which forms an electrostatic latent image on the respective image carriers, developing means which visualizes images by adhering toner on the electrostatic latent image formed by the charging and exposing means, transfer means which transfers the toner adhered on the electrostatic latent image onto an intermediate transfer body, and cleaning means which removes the toner adhered on the image carrier after the image carrier passing the transfer means have been disclosed. The cleaning means is provided with a plurality of cleaning members to act on substances adhering onto the image carriers and a plurality of feeding routes for the toner recovered by the cleaning members. One or more of the feeding routes are supply routes of recycled toner to a developing means. The route is selected for each cleaning member.
In the aforementioned method for reclaiming remaining-toner after transfer, the reclaimed toner which is collected by a cleaning means is subject to stress by the cleaning means and the developing unit, which deteriorates the powder characteristics and the charging characteristics. Thus, if a large amount of the reclaimed toner is supplied to the developing unit, photographic fog or cloud is generated. This is a problem.
Furthermore, in the conventional color image forming apparatus, another method, in which after the yellow (Y), magenta (M), cyan (C), and black (K) toner images are transferred, color-mixed toner remaining on the intermediate transfer belt or the photoconductor drums is collected by the cleaning means to be brought back to the black developing unit, has been proposed. However, if a large amount of color-mixed toner is supplied to the black developing unit, the black color changes. This is also a problem.
To solve these problems, methods have been proposed.
An electrophotographic copy machine that includes a photoconductor drum, a developing unit which develops a latent image on the photoconductor drum, toner density detecting means which is provided in the developing unit to detect the density of toner in the developing unit, cleaning means which recovers the residual toner on the photoconductor drum, a toner recovery container which receives discharge toner among the recovered toner, toner recovery means which collects the toner recovered by the cleaning means and unidirectionally discharges it, and switching means which is provided near an end of the toner recovery means to switch the carrying direction of the recovered toner have been proposed. When the toner density detecting means detects the density of the toner in the developing unit is a predetermined value, the switching means is switched so that the recovered toner is collected as the discharged toner. Then, the toner density detecting means performs the toner supplying operation to maintain a proper density of toner. When the supplied toner undergoes an agitating operation, regardless of output of the density of toner inside the developing unit obtained by the toner density detecting means, the toner recovered by the cleaning means is collected for recycling.
a method has been proposed that, when the density of residual toner on photoconductor drums after transfer or the density of toner inside a developing unit exceeds a predetermined value, a path for the toner is changed from a reclaiming path to a discharging path after a power source is turned on or after leaving the device as it is for a predetermined time.
Furthermore, an electrophotographic copy machine that includes a photoconductor drum, a developing unit, cleaning means, toner recovering means, a toner recovery container, first toner conveying means, second toner carrying means, and switching means have been proposed. The developing unit develops a latent image on the photoconductor drum. The cleaning means recovers residual toner on the photoconductor drum. The toner recovering means recovers toner in a predetermined conveying direction from the cleaning means. The toner recovery container accommodates toner for discharging. The first toner conveying means is provided on upper stream of the toner recovering means in the conveying direction so as to convey toner to the developing unit. The second toner conveying means is disposed on downstream of the toner recovering means in the conveying direction so as to convey toner to the toner recovery container. The switching means is disposed inside the toner recovering means so as to switch in accordance with predetermined number of copies between (a) conveying toner from the first toner conveying means and the second toner conveying means and (b) conveying toner from the second toner conveying means alone.
An electrophotographic device that forms an image on a photoconductor using a plurality of different kinds of toner by charging, recording, and developing, and transfers the formed image so as to perform recording on a sheet have been proposed. In the meantime, a cleaning unit removes and recovers residual toner on the photoconductor after the transfer. The electrophotographic device is provided with detecting means, which detects a mixing ratio of the recovered toner.